Wow, best of luck to you going back - It's tough to return to the grueling work of UPS after a seriouis injury and time off.
Your center may have gone to the PAS (preload assist system , I think). Stickers are put on every package telling the preloader where to put them in the pkg car. Instead of having the exact same load every day it may change according to volume and number of stops.
If you're not familiar with it you may be a bit baffled with the change. I'm not a driver so don't know how it really affects a driver's day. Maybe some drivers can offer something on that.